However, the Combine had realized such an attack to be a logical consequence of the Fourth Succession War, and had been preparing for it for the past years. The differences between the Combine in 3039 and the Capellans in 3028 were legion, and the strategic situation was decidedly different: this time, Davion did not have the advantage of having double agents in the highest ranks of the enemy military. The Draconis Combine Mustered Soldiery had also recuperated from the Fourth Succession War and the Ronin Wars much faster than anyone had anticipated, owing in part to a technological renaissance brought about by the Helm Memory Core. New 'Mech designs such as the Hatamoto-Chi, the Daboku and the CGR-1A9 Charger variant had been created in preparation for the expected attack.

Furthermore, Gunji-no-KanreiTheodore Kurita had created a neutral buffer state along two thirds of his realm's border with the Steiner realm by granting rebellious border worlds their freedom and allowing the Free Rasalhague Republic (FRR) to form. On the sidelines, this had forced House Steiner to also commit numerous contested worlds on their side of the border to the new state, thus nullifying their gains in the previous war. ComStar had actively supported the formation of the FRR and provided the DCMS with BattleMechs from their own stocks as an incentive, including (by error or by design) lostech equipment that had not been seen in the Inner Sphere for decades, if not centuries.

The War of 3039 was notable for being the first conflict in decades, if not in centuries, where vintage Star League-era technology provided by ComStar as well as new or rediscovered technologies were employed on any significant scale (discounting the use of HPG Fax "black boxes", and rare individual cases during the Fourth Succession War where double heat sinks, Triple Strength Myomer and the EW Equipment were employed in their experimental stages). Unfortunately the Allies were unaware of Gunji-no-Kanrei Theodore Kurita's secret deal with ComStar.

Listen-Kill Missiles saw their first widespread deployment in this conflict. However, the Draconis Combine not only reverse-engineered the new technology and used them against the attackers within a very short time; they were also quick to develop and distribute an ECM package to their frontline units that negated the effect of the L-K technology. When the technology was finally ready for mass-production in 3042, the ubiquity of the ECM technology had already rendered it largely useless.

The attack was apparently quite unimaginative, carried out with a conservative strategy that mostly relied on strength of numbers to exploit the Combine's perceived lack of fighting equipment. Theodore Kurita answered with a bold bluff. The Combine fought a delaying action, committing mostly conventional units to bog down the attackers while strong forces were committed to Operation Orochi, a quick counter-attack that captured several worlds including Quentin, an important 'Mech factory site. Operation Orochi was a gamble because it stretched the Combine's defenses to the limit and completely stripped rearward areas of any combat equipment, effectively exposing the Combine's flank to the onslaught. However, the bluff worked and the swift counterattack created the illusion of a much stronger military than the DCMS actually was at the time, augmented by the appearance of vintage Star League era equipment and entirely new BattleMech designs. It succeeded not only in forcing the attackers on the defensive, drawing units scheduled for assaults to defense assignments and thereby upsetting the invasion timetables; made insecure by these unforseen developments, Hanse Davion aborted the offensive and called an end to the War in 3040. It would be eleven years before he would find out that he fell for Theodore's bluff.

By March of 3039 all LCAF and AFFS units were in place for the coming invasion, however the leaders of the alliance still needed a casus belli, if only to placate potential domestic and international protest. The justification eventually seized upon were the violent actions taken by the Combine to suppress protests on former Davion worlds it had conquered; that these protests had been instigated and supported by the alliance was a minor detail. On April 15 Prince Hanse Davion made a public proclamation against this barbaric treatment of worlds it still laid claim to and that "steps must be taken to deal with the Kurita tyranny," even as units were already en transit or had even begun their assaults. The next day the war officially began when Steiner and Davion units made the jump into Kuritan systems.[1]

Although there had been no strategic surprise in this invasion as during Fourth Succession War, a measure of tactical surprise was achieved thanks to the alliance's use of the commercial-military command circuits to secretly assemble units at their jump-off positions. Additionally the sheer scope of the assault also caught the Kuritans off-guard as eight worlds were invaded in the opening phase of the first wave, most within the Dieron Military District and targeting in particular An Ting, New Mendham and Vega. Native garrison forces often melted away in the face of such serious opposition, while rivalries between front-line and militia units on worlds defended by both led to uncoordinated and ineffectual resistance. The situation worsened in late April as another sixteen worlds were attacked, again most from within the Dieron district, followed in early May when worlds of the Galedon and Benjamin districts were struck. By the end of the month over thirty Combine worlds were either under the control of or in the process of being conquered by the Steiner-Davion alliance.[1]

The DCMS commander structure was also in disarray at this point, and not just from the sheer shock of the assault and mass of fleeing civilians clogging up the shipping lanes. Cooperation was poor and conflicting orders were given by senior officers who supported either the traditionalist views of the Coordinator or the reformation views of his son. Over the next few weeks Kaneri Kurita did his best to blunt the invasion and regain the initiative, facing internal opposition especially in the Galedon and Bejamin districts. In the mean time the alliance continued to exploit this confusion by operating freely along the border and preparations were made to begin Wave Two in July.[1]

"Operation Winter Snow" was commanded by General Nondi Steiner and given the task of isolating the Dieron district from the rest of the Combine. It would accomplish this by attacking six worlds in the first wave, including the key prefecture capitals of Kessel and Vega, eventually linking up with the Dieron Thrust during the Second Wave to complete the isolation. Because it was the only thrust launched entirely from Commonwealth territory, it quickly became known as the Commonwealth Thrust. It was planned to take three months to complete the conquest of these worlds, and despite fierce resistance these timetables held, pleasing Lyran leadership and setting the stage for further victory.[2]

"Operation Storm Hammer", under the command of Hauptmann-GeneralIsabella Rahn, was the second of two thrusts aimed to isolate the Dieron district, striking at worlds in the Al Nair and Ashio prefectures before eventually linking up with the Commonwealth Thrust. While also under Lyran leadership, this 'Dieron Thrust' was instead primarily made up of mercenaries: nine regiments total combined with three regiments each from the AFFS, AFFC and LCAF. Of the nine worlds invaded only one was defended by front-line forces, thus LCAF command did not expect any serious opposition to their conquest. Instead it was important that the invaders quickly dig-in for the expected counter-attack, after which these worlds were expected to serve as jump-off points for follow-on invasions in the planned Second and Third waves.[3]

While no invasion was launched against the district capital of Dieron itself, various covert operations were conducted in and around the planet in preparation for a possible assault at a later date. These included attacks by LIC agents against military command and transportation infrastructure during the months of May and June. The most serious of these took place in June when companies of Lyran Marines sought to seize control of the system's nadir and zenith point recharge stations. The first attack on 10 June, against the Olympus station at the nadir point, was only just repulsed before the marines could take the command deck. The second attack on 13 June was against the zenith-point Bastion station, and attempted to use space debris aimed at the station which would force it's evacuation. This attack was only thwarted when the station's Helm-upgraded sensors detected and destroyed the space debris. Had these attempts worked, it was expected that the Davion Assault Guards, 33rd Avalon Hussars, 17th Donegal Guards, 3rd Royal Guards and Wolf's Dragoons would've been used to conquer the planet no later than during the Third Wave.[4]

Operation GAHERIS was launched in support of the Commonwealth and Dieron Thrusts, keeping Combine forces from coming to the aid of the Dieron district by striking into the Benjamin district. This operation was no less important though as, depending on how the battle went, the worlds conquered here could serve as staging points for an assault on Benjamin itself. Thus there was some trepidation when Field MarshalJames Sandoval was given overall command of the Benjamin Thrust. A political appointee, Duke Sandoval nevertheless was a proven commander and made a point to host a gathering of his subordinates at his family estate in improve relations and implement last-minute changes to the plan. Six worlds were attacked in the First Wave, and but for minor setbacks their conquest went as planned.[5]

Outcome: The Fed-Com operation on the planet started before the initial invasion. The High Command sent special operation teams to the world to train the local anti-Combine movement. The operatives found a solid resistance organization with some hundred military trained members. The mercenary command Lindon's Battalion was sent as reinforcements to the movement. The local Combine government was overthrown and with the assistance of the special forces the militia was devastated. Any further resistance by the militia was crushed by the mercenary command. [6]

Outcome: The planet was the symbol of a great loss of Combine honor against the Fox in the early 31st century. Prince Hanse Davion knew how important it was to support the local resistance movement with equal material and men. Dozens of intelligence operatives and Special Operation Teams prepared the world for the coming liberation. Several months before the War started the movement together with the SpecOps attacked important Combine locations and personalities. The DCMS reacted with an increase of the local military presence. The Fed-Com side reduced their level of activity to lure the Dragon into a sense of false security. With the arrival of the Clifton's Rangers command the guerrillas had the strength to get control over the planet. The mercenaries were supported by six battalions of volunteers which had removed all evidence of their Fed-Com affiliation. The local Combine leader was killed together with most of the high-ranking DCM officers. The units of the defenders chose to inflict damage and to die or surrender to the Fed-Com units. [7]

Outcome: The world was unremarkable place for both sides. The task to conquer Thestria fell to both regiments of the Dioscuri. The AFFS provided the commanding officers with all available information about the planet but the data were 15 years out of date. The initial landing was uncontested. Pollux annexed three important cities with large quantities of food because their sister unit get control about an important transport hub. The Thestrian militia was well prepared and dealt the mercenaries several losses. The supporting AFFS infantry occupied the cities which freed the 'Mech formations to hunt the guerrilla forces. In the end the DCMS forces could only delay the invaders. The mercenaries prepared their position for the coming counter attack of the DCMS.

Though focusing the bulk of efforts on Operations Winternee and Sturmhammer, the Lyran Commonwealth also ordered the Killer Bees and Knights of St. Cameron mercenary units to launch deep raids across the neutral Free Rasalhague Republic into the Combine, an attempted distraction to keep the DCMS off-balance and try and prevent troops posted in Alshain and Pesht Military Districts from redeploying quickly to the main front. Setting out as as early as a month before the first invasion wave was launched, the mercenaries struck deep in the Combine before finally withdrawing as the second wave faltered in the face of Combine counter-attack.[8]

Inspiring wide-spread fear in the Combine's civilian population as the mercenaries struck numerous worlds on the most direct paths to important targets such as Pesht and Buckminster, on the surface the raids did succeed in prompting a redeployment of Combine troops to better protect Alshain and Pesht, but in many cases the DCMS merely transferred less seasoned troops into the region as more proficient ones were moved to help repulse the Allies invasion thrusts. The raids also damaged relations between the newborn Free Rasalhague Republic and the Lyran Commonwealth, the Republic Riksdag and the Elected Prince lodging diplomatic protests regarding the Lyran's violation of their neutrality.[8]

Almost as soon as the first Lyran forces crossed the border, the DCMS enacted several contingency plans to redeploy troops from the interior to counter-attack or oppose any further advances, but they were designed more to oppose heavy raids in force rather than full invasion. As the sheer scale of the combined FedCom thrusts became clear, the bulk of the DCMS was shocked into virtual inaction by the overwhelming opposition they faced, practically confirmed by the Coordinator's desperate "Hold at All Costs" defensive orders.[9]

Not all heeded the Coordinator's orders, a few units choosing to adopt an exceedingly liberal interpretation of them and launch offensive strikes to try and convince the Lyran and Davion forces to delay any further thrusts. Similar to the Lyran mercenary deep strikes, the 4th Arkab Legion and the 11th Alshain Regulars launched raids in the Lyran Commonwealth that did little material damage but forced the LCAF to expend resources to hunt them down. The most notable however was the counter-raids launched by the Dieron based Ryuken regiments at the direction of Tai-shu Michi Noketsuna.[9]

While the Ryuken's attacks against New Earth, Procyon and Saffel would prove highly successful, thanks to lackluster intelligence reports their strike against Caph would prove near disastrous after the Ryuken-ni and Ryuken-san were shocked to discover two additional elite AFFS RCTs and, in possibly the greatest irony of the war, the Wolf's Dragoons were on-world. With the outnumbered Ryuken quickly surrounded, a bold and risky strike at a isolated AFFS staging base hidden in radioactive wastelands broke the stalemate and gave them to opening to escape off-world. Though little more than a footnote in the history of the war, the fighting did serve a cathartic purpose for both the Ryuken and the Dragoons, helping to lay the demons of Misery to rest.[9][10]

Outcome: The DCMS sent two units to recapture the planet from the LCAF. Before the invasion force arrived the remaining DCMS units on the ground supported by the ISF started a guerrilla campaign. The relocation of the 1st Argyle Lancers weakened the position of the Guards further. Further developments such as supply shortages and a hostile population made the situation worse. During the landing of the DCMS troops their DropShips were lightly damaged by the defending fighter force but no losses were recorded. The DCMS commands landed over 100 km away from the Lyran troops. The Guards launched a battalion-sized assault but were surprised by the strong defense. The Alshain Regulars held the line with their main force and sent only scout elements after the retreating Guard units. The 26th Guards waited for the final assault in the planetary capital. The 1st Sun Zhang Academy Cadre tried to sneak into the defensive perimeter but were discovered by a patrol. The commanding officer sent a hastily-assembled force to counter the move when the 6th Regulars began their assault. The Lyrans retreat further. The Dragon tried 5 times to break the defense but were always beaten back. When the Commanding officer together with many of his staff was killed by an car bomb the decision had fallen to retreat back to Lyran space. [11]

Unlike the other first wave thrusts, operations on the seven worlds targeted for mercenary-supported revolutions generally succeeded in taking the pro-Davion and under-defended worlds in short order, the only sticking point being the Davion military intelligence's failure to discover the presence of the Ryuken-yon on Harrow's Sun, stymieing all attempts to solidify control. That changed little with Combine counter-attack. While the Kanrei actively directed his troops to strike at every world targeted by the Allies, with the DCMS were already dangerously overextended to support OROCHI, the seven worlds taken by the Davion mercenaries were mostly ignored. Aside from the ongoing fighting on Harrow's Sun, only two came under direct attack, the Combine ultimately successfully in retaking all three. [12]

By the time the Combine had the resource to strike at the others, the War had effectively been concluded and the dug-in and reinforced mercenaries were able to repulse any DCMS raids and keep their charges in Davion hands, save for Galtor III. Miscommunication during the Allies recall resulted in Clifton's Rangers digging in despite the AFFS believing they had retreated, the FedSun government secretly supporting the world despite it being in Combine-held space after learning of this. However when the Combine realise they had "lost" Galtor III in the midst of sensitive POW negotiations, the FedSun government ordered the Rangers to pull out to try and avoid a diplomatic incident. Refusing to abandon the world, the mercenaries broke contract to remain behind before being destroyed in 3042 after a bitter 15 month defense, one and a half years after the War of 3039 nominally concluded, when the Combine sent three front-line regiments to brutally subjugate Galtor III. [12][13]

Even with the tragic and contentious loss of Galtor, ultimately the mercenary actions were among the Allies most success, accounting for three of the seven worlds gained by the Federated Suns. [12]

Coinciding with the Kanrei's Operation OROCHI, Tai-shu Noketsuna on Dieron received intelligence that Operation STURMHAMMER commander Field Marshal Vanessa Bisla had ordered additional forces advance from their bases in the Terran Corridor to join the Dieron thrust, prompting him to send forces to take advantage of the redeployments. More a continuation of the Dieron raids launched during the first wave than a direct adjunct to Operation OROCHI, the strikes against the high-risk targets of Formalhaut and Quentin would prove wildly more successful than expected, with the 36th and 40th Dieron Regulars able to capture and hold both planets until the conclusion of the War and the signing of the Exeter Accords. The capture of Quentin and Independence Weaponry, the seat of the Federated Suns assault 'Mech manufacturing, would prove to be the Combine's biggest prize of the conflict and more than mitigate the worlds lost to the FedCom forces. [14]

While not directly involved in the defense of the Combine, the Free Worlds League and Capellan Confederation both sought to take advantage of Lyran and Davion preoccupation elsewhere to launch raids and strikes against the future Federated Commonwealth.

As the War of 3039 formally began, the Free Worlds League was in the final stages of ten-year long Andurien Secession, the bloody conflict to bring the Anduriens back into the fold helping to foster an increased sense of pride and nationalism in many League units. With this increased pride also came a desire to avenge the League's embarrassing defeats in the Fourth Succession War, making the raids that followed a forgone conclusion. [15]

Still heavily engaged in the Andurien conflicts, the initial League strikes were relatively small scale raids within the final weeks of the Allies first wave, the most extensive and successful being the recapture of Menkalien. In a rare intelligence coup, SAFE alerted the FWLM to the withdrawal of the LCAF garrison on Menkalinen shortly before the outbreak of war, FLWM troops retaking the world within six days. While SAFE ensured the recapture of Menkalien, it failed the 2nd Oriente Hussars on their so-called "Phact Finding" mission. Striking Old Kentucky, Chamdo and Reballa after the transfer of their frontline forces to the Kurita front, the Hussars ran into a frontline LCAF RCT on Phact itself, resulting in an epic three week chase before they could escape on July 10th 3039.[15]

The most surprising of these raids however was the 9th Marik Militia's impromptu strike against the important Liao world of Capella on July 12th. Deployed to extricate the 2nd Oriente Hussars from Phact, when the Hussars escaped on their own, the 9th's CO decided to launch "raid in force" against regional capital, inflicting heavy losses against the unprepared Blandford's Grenadiers before withdrawing in good order. [15]

Emboldened by the relatively success of their raids during the Allies first wave, the FWLM High Command made the fateful decision to launch invasions against six additional worlds during the FedCom forces planned second wave, seeking to capture or re-capture them for the League. Unfortunately the League military incorrectly assumed they would face minimal to no resistance, unaware of the DCMS counterattack and that the Allies postponement of many of their strikes had freed up numerous units to repulse their attacks. [16]

In most respects the Hsien, Alioth and Cor Caroli invasions of July to September 3039 were relatively successful, and the troops assigned able to flee ahead of the returning LCAF and AFFS forces. The League forces that assaulted Callison and Marcus were not so lucky, grossly outnumbered and outclassed, they suffered heavy losses as they were ejected by October. The most infamous however was the reborn Black Widow Battalion's total rout of the 18th Marik Militia on Hall on Christmas Day 3039. Cementing again Natasha Kerensky's fearsome reputation, though nobody in the Inner Sphere realised it at the time, the fighting on Hall was a preview for the future, the first instance of a Clan-style Cluster defeating a Star League-configured regiment. [16]

Much like the Free Worlds League, the Capellan Confederation had regained a measure of pride when it successfully repulsed the combined Andurien-Magistrcy invasion and also considered taking advantage of the distraction of the invasion of the Combine to launch raids into Davion-held space. Unfortunately the increased paranoia in the wake of ChancellorRomano Liao's ascension left the Strategios too scared to take its own initiative, fearful the Chancellor would either order their execution for their presumption if the raids failed or rashly order a full invasion of the Federated Suns if they proved successful. Recognizing they needed somebody with both a good personal relationship with the Chancellor as well as the wherewithal to actively launch the raids, the Strategios approached Archibald McCarron of the famed McCarron's Armored Cavalry. With the Big MAC uneasy at the restful period following the Andurien invasion, McCarron needed little prompting to be convinced to launch a series of deep raids into Davion space in May 3039. [17]

In total eight relatively minor Federated Suns worlds were targeted over the next several months as the Cavalry's hit-and-run raids extended deeper into the Davion space towards the important factory world of Kathil. Spending little over a week on each world inflicting as much damage as possible, initially the AFFS forces assumed the MAC would attempt to hold their worlds, leading to a confused response. However, after the AFFS realised the goal of Big MAC's strike was Kathil, Duke Morgan Hasek-Davion dispatched CASE JULIET, his own counter-invasion force, and set a trap for the mercenary unit on-world.[17]

Landing first on September 2nd, Barton's Regiment were outnumbered but unconcerned, striking at the seemingly sluggish 8th Syrtis Fusiliers while awaiting the other MAC regiments. Holding back until after the First and Third MAC landed, the Davion forces sprung their trap, revealing the Alcyone CMM and 1st Kittery Borderers were also on-world. Now heavily outnumbered, the shocked MAC held out for few more days before conceding they were over-matched. As the fighting on Kathil bogged down, Archie McCarron learned of the FedCom strike against their homeworld of Menke and immediately recalled the bulk of his troops, but gave an unsatisfied Colonel Marcus Barton authorisation to continue to operate behind enemy lines as he saw fit.[17][17][18]

Barton ultimately opted for a totally unexpected and highly questionable attack against Addicks, the command center of the entire Addicks PDZ. With Addicks a major staging point for units taking part in the invasion of the Combine, Barton easily concealed his two 'Mech Battalions among the multiple RCTs and regiments on-world. Painting his forces to resemble some of the Davion units stationed on Addicks, Barton's forces launched their attack on November 14th, rampaging through the spaceport for three and half hours before making a break for their DropShips, escaping but suffering extremely heavy losses in the process, most notably a Union-class DropShip with all hands and a JumpShip whose KF drive burned out after a desperate quick-charge.[17][19]

After their eventual return, McCarron's Armored Cavalry were hailed as heroes by the Capellan media, boosting the morale of the Capellan military at the cost of the AFFS counter-invasion and the damage it inflicted.[17]

While the McCarron Armored Cavalry raids reaching as deep as Kathil came as a surprise, Capellan March commander DukeMorgan Hasek-Davion had been making preparations for CASE JULIET since 3038 in case the Capellans chose to test if the AFFS had weakened itself to strike House Kurita. Originally a retaliatory strike against vital manufacturers on Grand Base, Victoria and Menke, Sarna March commander GeneralRoman Steiner also prepared to target Ares after consulting wih Hasek-Davion and the AFFS high command as well.[20]

Though highly risky as JULIET involved almost all the available Capellan March defenders, Duke Hasek-Davion and General Steiner knew a simultaneous strike of this magnitude would send a clear message to the Chancellor and rebuke McCarron for his raids. Demonstrating to the CCAF the weakness of its defenses, a lesson some considered possibly better saved for a renewed war against the Confederation, Hasek-Davion considered it a price well paid to prevent a larger Capellan strike during the War of 3039.[20]

The Confederation however found the price bitter indeed, suffering much greater physical losses compared to those inflicted by the Big MAC on the Federated Suns. The Capellan leadership would spin MAC's victories for a morale boost, "proving" that the Davion military was not invincible, publicly hiding the fact that military production on all four worlds had been crippled for months if not years.[20]

The failure of the LCAF and AFFS to properly coordinate their offensive led to the decision to integrate the military forces of the two nations well before they officially became one nation. House Kurita also won a symbolic victory with their conquest of Quentin where Independence Weaponry produced the Davion-favorite Victor. Following the loss of that factory world, the AFFC had to import their Victors from the St. Ives Compact.

But the Combine victory was not without cost. Though the Kanrei dragooning of the Combine's merchant shipping made Operation Orchi possible, it had a devastating effect upon the realm's economy.